The invention relates to ultrasonic imaging systems, and more particularly to systems that utilize a transducer probe to send ultrasonic signals to a remote ultrasonic imaging system.
The users of medical ultrasound transducer probes, hereinafter referred to as sonographers, can access bodily regions to be imaged via their free hand physical manipulation, rotation, sliding and tilting of the transducer probe. One area in particular where this manipulation is more challenging is transesophageal cardiac imaging. During transesophageal cardiac imaging, the sonographer orients a scanhead at the tip of the transducer probe in the esophagus or stomach of a patient in order to obtain different fields of view of the heart. To obtain the desired views of the heart, the sonographer may have to slide, twist or curl the transducer probe in order to properly position the scanhead, which contains the imaging transducer(s).
For this application, it has been found desirable to rotate the transducer contained in the scanhead independently from the scanhead itself. In combination with the ability to slide, twist or curl the scanhead, the ability to independently rotate the transducer(s) while the scanhead is stationary gives the sonographer the ability to obtain an ultrasonic image of any image plane orthogonal to and intersecting the face of the transducer(s) at each location to which the scanhead can be moved. By giving the sonographer the ability to remotely rotationally orient the acoustic device in the scanhead to obtain different image slices of the heart or its valves, for example, patient comfort is increased. Further, the time required for an ultrasonic examination may be reduced.
Devices are known that incorporate a remotely rotationally adjustable transducer. For example, U.S. Pat. No. 4,543,960 to Harui et. al. discloses a transesophageal echo cardiography scanhead. The elements of the transducer are mounted upon a rotatable base, which is connected by a shaft to a pulley below the transducer. A control cable is directed into the scanhead and is attached to the pulley. The elements of the transducer are electrically connected to a wire bundle by flexible PCB interconnects. The control cable is guided, through a pair of guide tubes, out of the scanhead so that the operator can control the angular relationship of the transducer with respect to the housing.
A disadvantage of the Harui device is that the pulley, shaft and flexible PCB interconnects require a considerable volume within the scanhead. It is desirable to maintain a minimum profile scanhead so that the scanhead may be easily inserted into the body and manipulated therein without causing excessive patient discomfort.
A further disadvantage of the Harui device is that, during rotation of the transducer, bending and axial stresses act upon the flexible PCB interconnects. In addition, the striking of the inner wall of the scanhead by the flexible PCB interconnects during rotation may cause the interconnects to buckle, jam and/or abrade. Because these devices generally cannot be repaired on site if broken and can cause major disruptions for their users and subjects if they fail while inserted in a patient, it is desirable to maximize the reliability of such rotatable probe devices. Additionally, with the device described, the flexible PCB interconnects may not act efficiently as thermal conductors. It is desirable to conduct heat away from the transducer(s) during its operation to avoid a "hot spot" on the scanhead in the lens area above the transducer, which could produce patient discomfort.
Another device incorporating a remotely rotationally adjustable transducer is disclosed in U.S. Pat. No. 5,176,142 to Mason. Mason describes using a rotating cable to drive a gear train within a scanhead of a probe. The gear train rotates a shaft-mounted transducer support structure. The transducer array is linked to conductors connected to the remote imaging electronics by a flex cable assembly. A first portion of the flex cable assembly is embedded in an acoustic damping material, which fills the volume within the support structure. The flex cable assembly protrudes out of the damping material, through an opening in the support structure, and extends around the support structure in the form of a loop. The loop portion of the flex cable assembly becomes straight and extends into a rear volume within the scanhead. In the rear volume, the flex cable assembly is formed into a spiral, which is wrapped around and attached to a stationary post.
A disadvantage of the Mason device is that the flex cable assembly is subjected to bending and axial stresses as the transducer array is rotated by the gear train, and the flex cable assembly may buckle, jam and/or abrade as it is ejected into or pulled from the rear volume. Additionally, the flex cable assembly and the shaft present acoustic discontinuities within the acoustic damping material. It is desirable to minimize acoustic discontinuities in the damping material and to minimize the worst bending excursion, axial buckling potential and abrasion experienced by any portion of the flex cable assembly. Further, the Mason device contains a complex gear train that occupies substantial space within the scanhead and may produce particulate debris that may interfere with the operation of the device.
Accordingly, it would be desirable to have an improved remotely rotationally-steerable medical ultrasound transducer device.